Ligand-metal coordination complexes, e.g., organometallic complexes, are useful as catalysts, additives, stoichiometric reagents, monomers, solid-state precursors, therapeutic reagents and drugs. Complexes of this type ordinarily are prepared by combining a ligand with a suitable metal compound or metal precursor in a suitable solvent at a suitable temperature. The ligand contains functional groups that bind to the metal center(s), remain associated with the metal center(s), and therefore provide an opportunity to modify the steric, electronic and chemical properties of the active metal center(s) of the complex.
Certain ligand-metal complexes are catalysts for reactions such as oxidation, reduction, hydrogenation, hydrosilylation, hydrocyanation, hydroformylation, polymerization, carbonylation, isomerization, metathesis, carbon-hydrogen activation, carbon-halogen activation, cross-coupling, Friedel-Crafts acylation and alkylation, hydration, dimerization, trimerization, oligomerization, Diels-Alder reactions and other transformations. In the field of polymerization catalysis, in connection with single site catalysis, the ligand typically offers opportunities to modify the electronic and/or steric environment surrounding an active metal center. This allows the ligand to assist in the creation of possibly different polymers. Group 4 metallocene based single site catalysts are generally known for polymerization reactions.
One application for metallocene catalysts is producing isotactic polypropylene. Isotactic polypropylene and its production has been extensively studied. See, e.g., US 2004/0005984 A1.
In view of the industrial importance of this field, it would be desirable to have additional synthetic methods for the preparation of ligands.